chore: validate email addresses with dns

scripts/email_checker.go

@@ -0,0 +1,55 @@
+package main
+
+// Usage example:
+// cat emails.txt go run email_checker.go > result.txt
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"regexp"
+	"strings"
+)
+
+const MailPattern = "[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+"
+
+var mailRegex *regexp.Regexp
+
+func init() {
+	mailRegex = regexp.MustCompile(MailPattern)
+}
+
+func CheckEmailMX(email string) bool {
+	parts := strings.Split(email, "@")
+	if len(parts) != 2 {
+		return false
+	}
+	records, err := net.LookupMX(parts[1])
+	return len(records) > 0 && err == nil
+}
+
+func ValidateEmail(email string) bool {
+	return mailRegex.Match([]byte(email)) && CheckEmailMX(email)
+}
+
+func main() {
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		email := scanner.Text()
+		if email == "" {
+			return
+		}
+
+		if ValidateEmail(email) {
+			fmt.Printf("[+] %s\n", email)
+		} else {
+			fmt.Printf("[-] %s\n", email)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+}